Viral load

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Viral load

Viral load is a measure of the severity of a viral

Virus

A virus is a Optical microscope#Limitations of light microscopes infectious agent that is unable to grow or reproduce outside a host cell . Viruses infect all cellular life....
infection, and can be calculated by estimating the amount of virus in an involved body fluid. For example, it can be given in RNA copies per milliliter of blood plasma. Determination of viral load is part of the therapy monitoring during chronic viral infections, and in immunocompromised patients such as those recovering from bone marrow

Bone marrow

Bone marrow is the flexible biological tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells....
or solid organ transplant

Organ transplant

Organ transplant is the moving of an organ from one body to another , for the purpose of replacing the recipient's damaged or failing organ with a working one from the donor site....
ation.

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Viral load is a measure of the severity of a viral

Virus

Bone marrow

Bone marrow is the flexible biological tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells....
or solid organ transplant

Organ transplant

Organ transplant is the moving of an organ from one body to another , for the purpose of replacing the recipient's damaged or failing organ with a working one from the donor site....
ation. Currently, routine testing is available for HIV

HIV

Human immunodeficiency virus is a lentivirus that can lead to AIDS , a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections....
-1, cytomegalovirus

Cytomegalovirus

Cytomegalovirus is a Virus genus of the Herpesviridae group: in humans it is commonly known as HCMV or Human Herpesvirus 5 . CMV belongs to the Betaherpesvirinae subfamily of Herpesviridae, which also includes Roseolovirus....
, hepatitis B virus, and hepatitis C

Hepatitis C

Hepatitis C is a Blood-borne disease infectious disease that is caused by the hepatitis C virus , affecting the liver. The infection is often asymptomatic, but once established, chronic infection can cause inflammation of the liver ....
virus.

HIV viral load test

Several different HIV viral load tests have been developed, and three are currently approved for use in the US:

Amplicor HIV-1 Monitor test (Hoffman-La Roche), better known as the PCR
Polymerase chain reaction

The polymerase chain reaction is a technique widely used in molecular biology. It derives its name from one of its key components, a DNA polymerase used to amplify a piece of DNA by in vitro enzyme DNA replication....
test
NucliSens HIV-1 QT, or NASBA (bioMerieux)
Versant/Quantiplex HIV-1 RNA, or bDNA (Chiron/Bayer
Bayer

Bayer Aktiengesellschaft is a Germany chemical industry and pharmaceutical company founded in Barmen, Germany in 1863. Today it is headquartered in Leverkusen, North Rhine-Westphalia, Germany....
)

These tests have been approved by the Food and Drug Administration

Food and Drug Administration

The U.S. Food and Drug Administration is an Government agency of the United States Department of Health and Human Services and is responsible for regulating and supervising the safety of foods, dietary supplements, Medications, vaccines, Biopharmaceutical, blood transfusion, medical devices, Electromagnetic radiation-emitting devices, veteri...
in the United States

United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
for use in monitoring the health of people with HIV, in conjunction with other markers. Higher numbers in the viral load tests indicate an increased risk of getting sick from opportunistic diseases. These tests are also approved for monitoring the effects of anti-HIV therapy

Antiretroviral drug

Antiretroviral drugs are medications for the treatment of infection by retroviruses, primarily HIV. When several such drugs, typically three or four, are taken in combination, the approach is known as highly active antiretroviral therapy, or HAART....
, to track viral suppression and detect treatment failure. Successful combination antiretroviral therapy should give a fall in viral load of 1.5 to 2 logs (30-100 fold) within six weeks, with the viral load falling below the limit of detection within four to six months.

An affordable, largely manual test, which has the European regulatory approval for clinical use, is also used for viral load monitoring (ExaVir Load from Cavidi AB, http://www.cavidi.com). It depends on measuring virus-associated reverse transcriptase (RT) activity and can therefore detect all types and subtypes of HIV. The technology does not require sophisticated laboratories and can therefore make viral load testing more accessible in all parts of the world.

Viral load tests can also be used to diagnose HIV infection, especially in children under 18 months born to mothers with HIV, where the presence of maternal antibodies prevents the use of antibody

Antibody

Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacterium and viruses....
-based (ELISA

ELISA

Enzyme-Linked ImmunoSorbent Assay, also called ELISA, Enzyme ImmunoAssay or EIA, is a biochemistry technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample....
) diagnostic tests

HIV test

HIV tests are used to detect the presence of the human immunodeficiency virus in blood serum, saliva, or urine. Such tests may detect HIV antibodies, antigens, or RNA....
.

Persons with HIV are most contagious during the earliest stages of infection, when an antibody test would yield a negative result. Therefore, the importance of viral load testing is deemed important for yielding an earlier HIV diagnosis. Since persons are most contagious during early infection, widespread testing could provide significant public health benefits.

Results

The results of these tests are usually given as number of HIV RNA copies per milliliter (ml) of blood

Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
. The PCR test may give the number of HIV RNA copies per 0.05/ml, so one would multiply the result by 20 to get the standard result.